Insurance term · plain English
Anti-concurrent causation
A clause that lets the carrier deny the entire loss if ANY contributing cause is excluded — even if a covered cause did most of the damage.
What it actually is
Anti-concurrent causation (ACC) clauses sit in the exclusions section of most HO-3 policies. They typically read: "We do not insure for loss caused by any of the following ... regardless of any other cause or event contributing concurrently or in any sequence to the loss." So if a hurricane (covered) AND flood (excluded) hit at the same time, the ACC clause says the whole loss is excluded because flood contributed.
Why it matters for a claim
ACC is how a carrier converts a partially-covered loss into a full denial. About 43% of HO-3 denials we’ve audited in the beta cohort lean on ACC. The defense is to disaggregate the causes — show what damage came from the covered peril alone, BEFORE the excluded peril made things worse. That’s where forensic sequencing, weather records, and photo timestamps win or lose the claim.
Example
A wind storm tears shingles off the roof. Three days later, heavy rain enters the now-exposed deck and floods the attic. Carrier cites ACC and denies the whole interior water loss because "flood." Defense: show the wind damage happened first (NOAA records + neighbor photos timestamped before the rain), and the interior water came in through the wind-caused opening — so wind, not flood, is the proximate cause.
Apply this to your actual policy.
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